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Alloy hubs and bearings

loggyboy - 21/8/13 at 01:44 PM

Any hints on how to get these in?
I have mk2 escort/capri alloy hubs with bearings supplied with them. I tried tapping them in squarely with an old bearingt shell, but didnt get far. Not sure if pressing them is wise. or would it?
Suggestions welcomed.

Mr Whippy - 21/8/13 at 02:17 PM

I had these but didn't find it too difficult to chap the bearing shells in, you could try heating the hubs up in the oven and that should expand the bore and allow you to drop the shells in easily (without the bearings obviously as they'd get cooked)

loggyboy - 21/8/13 at 02:29 PM

Great idea. just happen to have an old oven in the garage for curing powdercoat so wont even have to get permission from the wife!

mcerd1 - 21/8/13 at 02:34 PM

I wouldn't heat the alloy any more than you had too (incase it affects any heat treatment - some alloys this is only ~100°C+)

but you could freeze the bearings overnight before fitting them

for most hubs I'd say the press is the best option, but thats for OE stuff not your fancy aftermarket bits....

[Edited on 21/8/2013 by mcerd1]

Mr Whippy - 21/8/13 at 02:48 PM

quote:
Originally posted by mcerd1
I wouldn't heat the alloy any more than you had too (incase it affects any heat treatment - some alloys this is only ~100°C+)

but you could freeze the bearings overnight before fitting them

Yip good point, doing both should help a lot

loggyboy - 21/8/13 at 02:55 PM

Also thinking about it more, heating the hub may expand it in all directions, closing up the gap for the bearing rather than opening! Either way, freezing the bearing shells is a good starting point.

mcerd1 - 21/8/13 at 02:57 PM

^^ the heat generally makes the hole a little bigger overall

but a lot of alloy's don't like getting to hot - even if the heat treatment is ok, you could end up warping it by releasing some of the residual stresses left from the machining, etc.....
(maybe I'm paranoid, but I wouldn't risk it on my own hubs)

also don't forget to use a little oil to help it in

[Edited on 21/8/2013 by mcerd1]

britishtrident - 21/8/13 at 03:19 PM

quote:
Originally posted by loggyboy
Also thinking about it more, heating the hub may expand it in all directions, closing up the gap for the bearing rather than opening! Either way, freezing the bearing shells is a good starting point.

A "hole" expands outwards when heated ie the diameter increases.

The bearings are a light interference fit to prevent them becoming loose when the hub gets warm and the alloy expands more than the steel bearing outer ring.

Also with an alloy hub you have to allow a little end float when adjusting to allow for expansion.

Even heat 100c to 120c for no more than 20minutes won't do to much harm to the heat treatment treatment.

[Edited on 21/8/13 by britishtrident]

theprisioner - 21/8/13 at 03:52 PM

I found a great way to get bearings out of hubs, had the same problem on my puma. Needed to retain the front hubs for the rear on the J15. New bearings of course supplied in the kit. You need a lot of cohonies and a friend with a plasma cutter:

1) Remove as much of the bearing as you can cage and inner roller. Brute force will suffice.

2) Switch on plasma cutter, turn down to minimum and cut across the bearing shell. Now with a lot of luck the breakthrough will be minimum and the shell will drop out.

Worked for me!

loggyboy - 21/8/13 at 03:57 PM

I need to get them IN not OUT?!

Mr Whippy - 21/8/13 at 04:16 PM

Heating the hub to 150 degrees is nothing, they get damn hot anyway being bolted onto the back of the brake disk.....honestly

Chuck the bearing shell in the freezer and heat the hub up, the shell will just drop in, I'm sure that was the instructions on my hubs anyway

mark chandler - 21/8/13 at 05:07 PM

Played a blow torch over my hub, bearing out the freezer and it dropped in with a clunk, 2 minutes later on immovable.

rusty nuts - 21/8/13 at 07:20 PM

quote:
Originally posted by theprisioner
I found a great way to get bearings out of hubs, had the same problem on my puma. Needed to retain the front hubs for the rear on the J15. New bearings of course supplied in the kit. You need a lot of cohonies and a friend with a plasma cutter:

1) Remove as much of the bearing as you can cage and inner roller. Brute force will suffice.

2) Switch on plasma cutter, turn down to minimum and cut across the bearing shell. Now with a lot of luck the breakthrough will be minimum and the shell will drop out.

Worked for me!

Not sure I would try doing it that way, too easy to end up with a scrap hub. A better way is to remove the inner race and bearings then use a MIG welder on high setting and run a bead around the inner bearing surface of the outer race then quickly turn the hub over to allow the remainder of the bearing to just drop out. Escort or Capri front hubs use taper roller bearings which are best fitted using a bearing drift which takes only a few seconds for each outer race.

Litemoth - 21/8/13 at 10:09 PM

My two penneth...

Don't go baking hubs or freezing your bearings - the metallurgical properties will be irrevocably changed and reduce the life of the hubs and bearings. The tolerances for most hubs don't require 'sweating' to get them to go together.

Push the outer races in with a press and some decent square tooling. If you haven't got one then get to one. Bashing them in with a hammer and a punch (yes, we've all done it) doesn't do bearings any good at all.

Wadders - 21/8/13 at 11:12 PM

Originally posted by Litemoth
My two penneth...

Don't go baking hubs or freezing your bearings - the metallurgical properties will be irrevocably changed and reduce the life of the hubs and bearings.

Flipping heck Litemoth, He's knocking together a toy car in a shed, not building the next space shuttle

britishtrident - 21/8/13 at 11:12 PM

quote:
Originally posted by Litemoth
My two penneth...

Don't go baking hubs or freezing your bearings - the metallurgical properties will be irrevocably changed and reduce the life of the hubs and bearings. The tolerances for most hubs don't require 'sweating' to get them to go together.

Push the outer races in with a press and some decent square tooling. If you haven't got one then get to one. Bashing them in with a hammer and a punch (yes, we've all done it) doesn't do bearings any good at all.

Care to explain to how sticking a alloy steel bearing in a domestic freezer will (permanently) change its' metallurgy ? -- fitting bearing parts by freezing using dry ice or liquid nitrogen is common practice in industry.

Likewise evenly heating aluminium silicon alloys to the 120c temperature for time suggested followed by natural cooling won't cause problems. In fact this is done all the time when replacing the valve guides in alloy heads. Some engine builders heat cylinder heads to 160c and some claim to go to 200c but I wouldn't go that high.

In this case the outer races won't just drift in the hubs are light alloy and require the the outer race to be an interference fit.
In the past some of designs of after-market alloy hubs sold for Ford stub axles have rendered the hub scrap after a few miles. The reason was when hot the differential thermal expansion between the outer race and the hub was so great allowed the outer race to rattle about loose within the hub

What will damage an alloy hub is bashing at it -- obviously the OP knew not do this or he wouldn't have asked.

Mr Whippy - 22/8/13 at 06:26 AM

quote:
Originally posted by Wadders
Originally posted by Litemoth
My two penneth...

Don't go baking hubs or freezing your bearings - the metallurgical properties will be irrevocably changed and reduce the life of the hubs and bearings.

Flipping heck Litemoth, He's knocking together a toy car in a shed, not building the next space shuttle

I'd be quite worried if your freezer was so cold it could destroy the property's of the bearings seeing that most only go as cold as a British winter

My ally hubs were certainly not heat treated and the metal was quite soft, tbh I would not like to have used them on a standard weight car as I reckon they'd bend on a pothole, I was actually replacing bent original steel ones.

[Edited on 22/8/13 by Mr Whippy]

britishtrident - 22/8/13 at 07:08 AM

Steel like any structural engineering material I can think of does become brittle at low temperatures but this ductile-brittle transition isn't permanent and is reversed as the material warms back up to the normal ambient range. This change from ductile to brittle can with just a small drop in temperature and cause unexpected instantaneous failures --- for anybody interested google on WW2 Liberty ships or T2 tankers.

In the case of a cheap poor quality steel the transition from having ductile mechanical properties to brittle can occur from 0c downwards, however with a high quality fine grained alloy steel that would be used for a bearing race I would expect the transition temperature to be much lower perhaps -50 to -60c way below what any domestic freezer can reach.

loggyboy - 22/8/13 at 07:44 AM

quote:
Originally posted by Mr Whippy
I'd be quite worried if your freezer was so cold it could destroy the property's of the bearings seeing that most only go as cold as a British winter

Its only the shell that needs go in, the acctualy bearings are seperate. I could understand if it was a massive temperature change, (going from oven, to freezer), but domestic freezer is only a few degrees below so probably not much colder than a freezing day in the heart of winter!

mcerd1 - 22/8/13 at 07:56 AM

^^ what BT said

to clarify why I was nervous about heating the alloy when I design structures out of the stuff we consider the normal temp. range to be -50°C to +70°C, but as BT says a higher temperature would need to be maintained long enough for it to start permanently changing the properties.
(don't get me started on Heat Affected Zones around welds etc....)

as for brittle fracture of the steel we design for -15°C and -25°C all the time (the standards let us go to -45°C if needed) its considered safe as long as you have a good enough quality of steel for the thickness of the material your using (the thicker it is the higher quality it needs to be) - bearings normally are made from good quality steel

I'd be more worried about the seals than anything else.... (and a domestic freezer isn't going to do much to them)

------------------------------------------------------------------------------------------------------------------------------------------------------ -----

now the more than you wanted to know bit

if you've ever bought steel for you chassis etc. you'll hopefully have noticed it comes in different grades
chances are you've been offered grade S235, this if bog std. european mild steel (235N/mm², the UK version of mild steel is S275 i.e. 17% stronger) or the other common one for box is S355 or 'high yield' steel

but whatever the yield strength of the grade unless it has a little suffix on the end like 'J0H' then its not been tested for brittle fracture and should not be used for any critical application
for tubes they are normally tested to either 'J0H' or 'J2H' and both are ok for structural use at least -35°C
for other sections the come in 'JR' 'J0' 'J2' (and 'K2' for some grades) (in order of worst to best) JR will do -15°C, J0 will do -35°C and J2 will do -45°C

also while I'm ranting on about grades - the same grade is often available to different BS standards:

for small tubes you will probably get offered 'cold formed' sections (only it won't say that, it'll just say BS EN 10219 on the certificate)
it has big corner radii and don't have the residual bending stresses relieved after they are formed (not bad as such, just not as good/reliable as hot finished ones)

the 'hot finished' (BS EN 10210) ones have smaller radii, lower residual stress and are better suited to welding on/near the corners - these are always best if its a safety/strength/stiffness critical application like a chassis

so if you want the best box sections for your chassis they should be grade 'S355-J2H'
(unless your using fancy seamless tubes etc - they have there own standards with different grades and qualities)

[Edited on 22/8/2013 by mcerd1]

Wadders - 22/8/13 at 08:37 AM

Here, straight from the horses mouth.......

http://www.timken.co.uk/EN-US/products/Documents/Industrial-Bearing-Maintenance-Manual.pdf

Litemoth - 22/8/13 at 12:19 PM

quote:
Originally posted by Wadders

Flipping heck Litemoth, He's knocking together a toy car in a shed, not building the next space shuttle

My sentiments exactly. No need for freezers and heaters on tiny hub bearings then .

I suspect that if it's that hard to push home then the 'limits and fits' on the bearing housing may not be to specification.

If you tell me what the bearing size is then I'll tell you what the bore tolerance is.

Litemoth - 22/8/13 at 12:27 PM

quote:
Originally posted by Wadders
Here, straight from the horses mouth.......

http://www.timken.co.uk/EN-US/products/Documents/Industrial-Bearing-Maintenance-Manual.pdf

The horses mouth says:

Never rapidly heat or freeze a bearing or bearing component.
Only use approved equipment, methods and controls to achieve
desired temperature.
Always follow OEM instructions to ensure bearings and rings are
properly positioned after heating or cooling.

....

loggyboy - 22/8/13 at 01:00 PM

It also says:

Cooling (Freezing)
Freezing standard class bearings and rings
•• -54°C (-65°F) - 1 Hour
Freezing precision class outer rings or cups
•• -29°C (-20°F) - 2 Hours
Note: This temperature can be obtained by commercial freezer/refrigeration
equipment.

It acctually says 54°C (-65°F) but this is blatantly a typo!

So minus 15 or 20 in a domestic freezer, couple with the fact that going from room temperature to what ever the freezer can achieve is going to be far from rapid.

Either way, an interesting selection of opinions, I will let you know how I get on.

[Edited on 22-8-13 by loggyboy]

b14wrc - 28/8/13 at 11:21 AM

I struggled to get my old Fiat coupe hub bearings out, ended up needing a 10 tonne press at a local garage to remove them, the guy had a struggle with them.

I had used the hammer method and made a right mess of it, leaving just the outer race totally wedged!

I have not replaced them yet with new ones, but expect they will need pressing in - hubs are steel though, not alloy.

Rob

loggyboy - 28/8/13 at 11:28 AM

The freezing alone trick didnt work, they must not have shrunk by much, if at all, in my domestic freezer. Didnt try the heating. at the mo ive tapped them in a mm or 2, stopped going further till i decide to continue hammering, remove and try heat for hubs AND freezing of shells, or to take them to my mates garage and press them.

I found the rear steels ones very easy (see the build thread update).

The old ones came out with a drift and hammer, and the new ones when it with a small hammering to get them started and pressed them the rest of the way with a vice.
I think alot depends on the type of bearing. Tapered go in easier as you only have to be rough with the shell.

Mr Whippy - 28/8/13 at 12:02 PM

So are the bearings in yet????

Freezing the steel is a waste of time anyway unless you have liquid nitrogen at hand as they shrink a tiny amount. Heating the hubs up in the oven is the correct way as the aluminium expands a lot. The shell would then just drop in.

Can't believe how many comments there were about the mysterious if not mystical changing of the metals property in a domestic oven, seriously it's just a car wheel hub

Litemoth - 28/8/13 at 02:14 PM

Press them in.

As I said, heating and cooling will often stress-relieve bearings (especially cheap Chinese ones). Bearings are ground to microns (0.001mm) accuracy and any upset (thermal or impact shock) will cause them to change shape and fail sooner than necessary...as will bearing housings that are out of shape or too tight.

There are stories that some of the alloy hubs being way out of tolerance though (often oversize)

Mine took about 3-4 Tonne to push into my alloy housing. A Fiesta rear (double bearing) I did recently took 10 tonne to push out and about 6 to push back in (std road car with steel bearing housing)

Driving them in with a hammer and a drift wouldn't have been an option

.

britishtrident - 28/8/13 at 03:47 PM

quote:
Originally posted by Litemoth
Press them in.

As I said, heating and cooling will often stress-relieve bearings (especially cheap Chinese ones). Bearings are ground to microns (0.001mm) accuracy and any upset (thermal or impact shock) will cause them to change shape and fail sooner than necessary...as will bearing housings that are out of shape or too tight.

There are stories that some of the alloy hubs being way out of tolerance though (often oversize)

Mine took about 3-4 Tonne to push into my alloy housing. A Fiesta rear (double bearing) I did recently took 10 tonne to push out and about 6 to push back in (std road car with steel bearing housing)

Driving them in with a hammer and a drift wouldn't have been an option

.

If you seriously think heating any steel to sub-200c temperatures will stress relieve or make any other difference to any steel you are pretty wide of the mark For the types of steel used for bearings (istr 1% Carbon + 0.45% Mn + 1.4%Cr) once it has been heat treated hardening by quenching from 850c then tempered by reheating to a lower temperature and slow cooling nothing short of 500c will have any effect, the stress relief temperature would be in the order of 650c held for along period.

loggyboy - 28/8/13 at 09:27 PM

All done, heated the hubs and they did almost fall in, just the lightest of persuasion. I didn't heat the bearings anyway, although the shells would have had some heat transferred to them but I'm sure they will be fine.